Gas-fired cooking device with griddle surface heated by heat bank

ABSTRACT

A more uniform heating of a griddle surface of a gas-fired cooking device is provided by a plurality of heating chambers disposed below the griddle surface, with each of the heating chambers heated by at least one naturally fed gas burner. A portion of the hot combustion gases rise into upper zones associated with each heating chamber that have relatively low average front-to-back air flow therein. The upper zones have sidewalls and downwardly extending dam walls that cooperate to create the low flow zones beneath the griddle surface. The relatively low flow rates within the low flow zones allow a more uniform layer of hot combustion gases to be formed along the underside of the griddle surface, thereby more evenly delivering heat to the griddle surface. There may be two or more such heating chambers.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of gas-firedcooking devices, and specifically to a gas-fired cooking device thatincludes a heat bank to provide a more uniformly heated cooking surface.

Gas cooking devices, such as gas-fired griddles, commonly utilizemultiple burners located in various locations beneath the heatedsurface. Air and fuel, such as natural gas, propane, or the like, areprovided to the burners, which bum the fuel to create hot combustiongases. Because each individual burner provides hot combustion gases to alimited area, the heated surface may develop hot and cold zones. Forinstance, hot zones typically develop directly over each burner and coolzones develop between the burners. Such uneven heating may lead toundesirable cooking results. As such, there is a need for an apparatusthat combusts gas in such a way as to provide a more uniformly heatedsurface, resulting in improved cooking performance.

SUMMARY OF THE INVENTION

The present invention provides a more uniform heating of a griddlesurface of a gas-fired cooking device. A plurality of heating chambersare disposed below the griddle surface and include a lower zone and anupper zone. Each of the heating chambers is heated by at least onenaturally fed gas burner generally disposed in the corresponding lowerzone. The gas burners generate hot combustion gases, a portion of whichrise into the corresponding upper zone disposed between the lower zoneand griddle surface associated with each heating chamber. The upperzones have sidewalls and downwardly extending rear flow-restrictingwalls, or dams, that cooperate to create a zone of relatively stagnantflow beneath the griddle surface. The relatively low averagefront-to-back flow rates within the upper zones allow a more uniformlayer of hot combustion gases to be formed along the underside of thegriddle surface, thereby more evenly delivering heat to the griddlesurface. In some embodiments, the vertical depth of the upper zones isdeliberately varied, from deeper to thinner moving laterally in towardthe center of the griddle surface. There may be two or more heatingchambers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of one embodiment of a gas-fired cookingdevice according to the present invention.

FIG. 2 is a partially exploded view of the gas-fired cooking device ofFIG. 1.

FIG. 3 is a sectional side view of the gas-fired cooking device of FIG.1 showing illustrative air/combustion gas flows.

FIG. 4 is a top view of a floor plate showing possible locations ofsecondary flow holes therein.

DETAILED DESCRIPTION OF THE INVENTION

While the cooking devices 10 according to the present invention may begas-fired griddles, braising pans, or what are sometimes referred in thefield as “skillets,” a griddle will be used as an exemplary cookingdevice 10 for simplicity of illustration, without limiting the inventionthereto. As shown in the Figures and described more fully below, thegriddle 10 utilizes a plurality of upper zones 40 having relatively slowmoving hot combustion gases therein and located below the generallyplanar surface to be heated 12 to help provide uniform heating to thesurface 12. The upper zones 40 are created by flow-restricting walls42,46 that act to create a hot air pocket in the upper zone 40, asdescribed more fully below.

The griddle 10 generally includes an outer housing 14 with a generallyplanar surface to be heated 12. Because it is common, but not necessary,for food to be placed directly on the surface 12 for cooking, thissurface 12 is sometimes referred to as the “cooking surface” or the“griddle surface.” The cooking surface 12 is shown as being smooth, butthe cooking surface 12 may optionally include one or more grooves as isknown in the art.

A plurality of generally front-to-back heating chambers 20 are disposedwithin the outer housing 14. The heating chambers 20 shown are disposedin a laterally adjacent configuration, meaning that they generally runfront-to-back and are disposed in a left-to-right series. Laterallyadjacent heating chambers 20 are not required to “touch” each other(e.g., share a common intervening wall 44), although such an arrangementmay be advantageous.

Disposed generally within the heating chambers 20 are respective gasburners 22. These burners 22 use a natural, unforced, draft for supplyair; as such, they are of the type generally referred to as “naturallyfed gas burners.” Such burners 22 are to be contrasted with forced airburners that utilize a forced air stream (or air/fuel stream), such asone generated by a fan.

The outer housing 14, burners 22, cooking surface 12, and controls (notshown) may be generally similar to those of the model SGS-36, sold bySouthbend of FuquayVarina, N.C., a division of Middleby-Marshall, Inc.of Chicago.

Each heating chamber 20 includes a lower or burner zone 30, where thehot combustion gases are generated, and an upper or low-flow zone 40disposed above the lower zone 30 and below the underside of the cookingsurface 12.

The burner zone 30 is generally bounded by the floor plate 24 on itslower side, the corresponding sidewalls 44, and the underside of theupper zone 40. The upper zone 40 is generally defined by the undersideof the cooking surface 12 and flow-restricting walls, specifically afront dam wall 42, a rear dam wall 46, and sidewalls 44 associatedtherewith. At least the front dam 42 and the rear dam 46 are downwardlyextending, thereby extending generally away from the underside of thecooking surface 12. While the front dam 42 and the rear dam 46 may beperpendicular to the underside of the cooking surface 12, they are notrequired to be; for instance, the rear dam 46 may advantageously beangled towards the front of the cooking device 10 by 30°-45°. The reardam 46 may have a stepped lower edge, with a higher section 46 a and alower section 46 b. As shown in the Figures, the higher section 46 ashould be more centrally located with respect to the center of thecooking surface 12 than the lower section 46 b.

Also, as shown in the FIGS., the upper zones 40 of adjacent heatingchambers 20 may utilize opposite sides of an otherwise common sidewall44. Further, the front dam 42 and the rear dam 46 of the various heatingchambers 20 may simply be laterally different portions of respectivecontinuous wall elements if desired.

It should be noted that the upper zone 40 and the burner zone 30 areadvantageously generally of the same length and that there isadvantageously no restriction disposed between the zones 30,40 so that“vertical” flow between the zones 30,40 may be in an unrestrictedmanner.

Each heating chamber 20 preferably includes a floor plate 24 disposedbelow the respective burner element 22. The floor plate 24 mayadvantageously include a plurality of secondary flow holes 26, discussedfurther below. The floor plate 24 should be spaced upwardly from thebottom of the outer housing 14, so as to help provide an inlet plenum 50connecting an air inlet located at or near the rear of the griddle 10(not shown) with the heating chambers 20.

One or more gas supply lines 16 connect the burners 22 in the griddle 10to a supply of gas fuel, such as natural gas, propane, butane, and thelike. The gas supply line(s) 16 may be regulated in any manner known inthe art. In addition, while not shown, the griddle 10 should include thenormal complement of controls and user interface (e.g., switches, knobs,warning lights, display, etc.), as is known in the art. These controlsmay include a suitable number of thermocouples disposed on the undersideof the cooking surface, in corresponding protective grooves withthermoconductive paste if desired.

The flow through the griddle 10 may best understood with reference toFIG. 3. Fresh inlet air flows into the outer housing 14 at the rearportion thereof. The primary flow of the inlet air is forward throughthe inlet plenum 50, around the end of the floor plate 24, and to theburners 22. Note that the inlet plenum 50 may be a single plenum, withthe flow therein divided downstream into the respective heating chambers20, or may be a plurality of plenums 50, such as one for each heatingchamber 20. Note also that the inlet plenum 50 is a natural flow plenum,not a forced flow. The burners 22 mix the inlet air with the fuel in anymanner known in the art. This mixing may occur completely within theheating chamber 20, or may occur slightly upstream from the heatingchambers 20. The air/fuel mixture is burned by the burners 22 to producehot combustion gases. The hot combustion gases tend to rise within theheating chamber 20, but there is a significant front-to-back flow withinthe burner zone 30 caused by natural drafting. A portion of the hotcombustion gases flow relatively directly out the exhaust located at therear of each heating chamber 20. That is, a portion of the hotcombustion gases exhaust relatively directly out of the heating chamber20, through the opening between the bottom edge 46 a,b of the rear wall46 and the floor 24 and into an appropriate flue 18, as indicated byarrow A. Due to the natural drafting effect, this portion of the hotcombustion gas tends to be somewhat focused along the burner 22. While aU-shaped (or J-shaped) burner configuration as shown in FIG. 2 helpssupply heat to the cooking surface 12 with some degree of uniformity, ahot-fast flow through the burner zone 30 of the heating chamber 20 has atendency to create hot and cold zones on the cooking surface 12 withoutthe present invention.

In order to combat this, another portion of the hot combustion gasesgenerated by the burner 22 is at least transiently dammed within theupper zones 40 beneath the cooking surface 12. This portion of the hotcombustion gas follows the path indicated by arrow B.

This portion of the combustion gas flows up into the upper zone 40 andresides therein for an extended period of time. The extended stay in theupper zone 40 allows a more uniform layer of hot combustion gas totransfer its heat to the underside of the cooking surface 12, resultingin a more uniform heating thereof. When the “stagnant” combustion gaswithin the upper zone 40 has cooled, it descends below the lower edge 46a,b of the rear dam 46, joins the flow from the burner zone 30, and iscarried out the flue 18. The presence of the perimeter wall (front dam42, rear dam 46, and sidewalls 44) helps create the upper zone 40 wherethe portion of the hot combustion gases are at least temporarilytrapped. It should be noted that the terms “dammed,” “stagnant,”“trapped,” and the like are not intended to mean that the combustion gasenters the upper zone 40 and never exits, or even is necessarily helduntil the unit 10 is turned off. Instead, these terms are used toindicate that the average horizontal (front-to-back) flow rate throughthe lower zone 40 is relatively low, such as ten-fifteen percent or lessof the relatively high flow rate through the burner zone 30 (which may,for example, have an average horizontal flow rate on the order of 85±10ft/min). As such, the upper zone 40 may be thought of as a constantlyrecharging buffer zone that acts as a heat capacitor, or heat bank, thatfeeds heat to the cooking surface 12.

In order to more uniformly distribute the heat within the upper zone 40,it may be advantageous to have the upper zone 40 in a given heat chamber20 vary in vertical thickness. One way of achieving this is to have thefront wall 42 be a uniform large height, and have the rearflow-restricting wall 46 have a stepped vertical height with a shorter(shallower depth) section 46 a, and a longer (deeper depth) section 46b, as described above. In this manner, sub-zones may be created in theupper zones 40, with a higher (but still low) flow rate in one sub-zoneand a lower flow rate in another. Better results can be achieved if the“thicker” zones are located closer to the side extremes of the griddlecooking surface 12 and the “thinner” zones are located closer to themiddle of the cooking surface 12. Alternatively, if three or moreheating chambers are 20 used, the center-most heating chamber(s) 20 mayhave relatively shorter (shallower) rear flow-restricting wall 46, andtherefore a “thinner” upper zone 40, while the outer-most heatingchamber(s) 20 may have relatively longer (deeper) rear flow-restrictingwalls 46, resulting in “thicker” upper zones 40.

The burner 22 may not perform properly if there is insufficient freshair supply thereto along the length thereof due to the relatively lowflow upper zones 40 being located somewhat close to the burners 22. Thisis particularly true of the rear-most portions of the burner 22. Betterperformance may be achieved if a portion of the inlet air in the inletplenum 50 is allowed to enter the burner zone 30 via the secondary flowholes 26, as indicated by arrow C. The location and size of thesesecondary flow holes 26 is best determined by empirical testing. SeeFIG. 4 showing one suitable configuration for the location of thesecondary flow holes 26 on the floor plate 24, with at least some of thesecondary flow holes being located roughly in the front-to-back middleof the heating chamber 20. If secondary flow holes 26 are employed, itmay also be advantageous to locate a deflector above the hole 26 so asto more evenly distribute the air provided thereby.

The embodiment shown in the FIGS. includes three heating chambers 20disposed side by side. However, the present invention is not limitedthereto and is intended to encompass gas-fired cooking devices 10 havingtwo, three, four, or more heating chambers 20 with low flow upper zones40. As such, the gas-fired cooking device 10 may be relatively narrowwith only a few heating chambers 20 and corresponding burners 22, or maybe relatively wide (e.g., ten or more feet), with more heating chambers20 and corresponding burners 22. Also, configurations where a heatingchamber 20 has one lower zone 30 feeding hot combustion gas to multipleupper zones 40 are within the scope of the present invention. Likewise,there may of course be more than one burner 22 in the burner zone 30 ofeach heating chamber 20 if desired.

Suitable results have been achieved with three heating chambers,arranged as shown in FIG. 2; upper zones 40 with depths on the order ofone inch or more, formed by rear dams 46 of approximately 2⅜ length bentat approximately a 30° angle towards the front of the cooking device 10,and having an edge on the higher section 46 a approximately ⅞ inchshorter than on the lower section 46 b; front dams 42 of depth more thanthe rear dams 46; ⅝ inch diameter secondary flow holes 26 in the patternshown in FIG. 4; propane fuel; and J-shaped burners 22 of 30,000 BTUsize with a ported cross-over near the front.

Also, as pointed out above, the present invention may apply to a numberof cooking devices 10, and is not limited to what is traditionallycalled a griddle. Thus, while the terms “griddle surface” and “cookingsurface” have been used for surface 12, it is not required that thegriddle surface 12 be a portion of what is traditionally called agriddle, or even that the surface 12 actually be used directly forcooking food. For instance, the cooking device 10 may be what issometimes referred to as a braising pan, and the cooking surface may beused to boil water or to generate steam, which may in turn be used tocook food. All such arrangements are intended to be encompassed withinthe present invention.

Although the present invention has been described herein with respect toparticular features, aspects and embodiments thereof, it will beapparent that numerous variations, modifications, and other embodimentsare possible within the broad scope of the present invention, andaccordingly, all variations, modifications and embodiments are to beregarded as being within the scope of the invention. The presentembodiments are therefore to be construed in all aspects as illustrativeand not restrictive and all changes coming within the meaning andequivalency range of the appended claims are intended to be embracedtherein.

What is claimed is:
 1. A gas-fired cooking device, comprising: agenerally planar griddle surface to be heated; a plurality of generallyfront-to-back heating chambers disposed below said griddle surface, eachhaving a lower zone and an upper zone, said upper zone disposed belowsaid griddle surface and above said lower zone; each of said heatingchambers heated by at least one respective gas burner, fed by naturaldraft, generating hot combustion gases in said lower zone, at least aportion of said hot combustion gases flowing from said lower zone tosaid upper zone; each of said heating chambers having sidewalls anddownwardly extending flow-restricting walls that cooperate with saidsidewalls to create said upper zone for transiently retaining thereinhot combustion gases from said lower zone; said upper zone havingrelatively slow average front-to-back flow rate therein and said lowerzone having relatively faster average front-to-back flow rate therein.2. The device of claim 1 wherein said flow-restricting walls include afront wall and a rear wall, said rear wall having a first lower edgeportion spaced downwardly from said griddle surface a first distance anda second lower edge portion disposed farther from a center of saidgriddle surface than said first lower edge portion and spaced downwardlyfrom said griddle surface a second distance, said second distance largerthan said first distance.
 3. The device of claim 2 wherein both saidfirst lower edge portion and said second lower edge portion areassociated with one of said heating chambers.
 4. The device of claim 2wherein said first lower edge portion is associated with a first of saidheating chambers and said second lower edge portion is associatedanother of said heating chambers.
 5. The device of claim 1 wherein eachof said upper zones has a depth of not less than 1½ inches.
 6. Thedevice of claim 1 wherein the lower zone and the upper zone of at leastone of said heating chambers have substantially the same length.
 7. Thedevice of claim 6 wherein combustion gases from the lower zone of saidone of said heating chambers may freely flow into the correspondingupper zone of said one of said heating chambers in an unrestrictedmanner.
 8. The device of claim 1 wherein said cooking device is selectedfrom the group consisting of a griddle and a braising pan.
 9. The deviceof claim 1 including a plate generally bounding at least one of saidheating chambers on a lower side thereof, wherein said plate includes aplurality of flow holes therein for the inlet of secondary air into saidat least one heating chamber.
 10. The device of claim 9 wherein at leastsome of said flow holes have a diameter of approximately ⅝ inch and aredisposed in a front-to-back direction generally towards the middle ofsaid at least one heating chamber.
 11. A gas-fired cooking device,comprising: a generally planar griddle surface to be heated; a pluralityof generally front-to-back heating chambers disposed below said griddlesurface and having a respective burner zone and a respective low flowzone disposed below said griddle surface and above said burner zone;each of said heating chambers heated by at least one respective gasburner, fed by natural draft, generating hot combustion gases in saidburner zone, at least a portion of said hot combustion gases flowingfrom said burner zone to said low flow zone; each of said heatingchambers having sidewalls and downwardly extending flow-restrictingwalls that cooperate with said sidewalls to create said low flow zonebelow said griddle surface and above said burner zone for transientlyretaining therein said hot combustion gases from said burner zone. 12.The device of claim 11 wherein said flow-restricting walls include afront wall and a rear wall, said rear wall having a first lower edgeportion spaced downwardly from said griddle surface a first distance anda second lower edge portion disposed farther from a center of saidgriddle surface than said first lower edge portion and spaced downwardlyfrom said griddle surface a second distance, said second distance largerthan said first distance.
 13. The device of claim 12 wherein both saidfirst lower edge portion and said second lower edge portion areassociated with one of said heating chambers.
 14. The device of claim 11including a plate generally bounding at least one of said heatingchambers on a lower side thereof, wherein said plate includes aplurality of flow holes therein for the inlet of air into said at leastone heating chamber.
 15. The device of claim 14 wherein at least some ofsaid flow holes have a diameter of approximately ⅝ inch and are disposedin a front-to-back direction generally towards the middle of said atleast one heating chamber.
 16. A gas-fired cooking device, comprising: ahousing having a griddle surface defining a generally planar surface tobe heated; at least first and second heating chambers disposed belowsaid griddle surface and internal to said housing; a first gas burnerdisposed substantially within said first heating chamber and fed bynatural draft; a second gas burner disposed substantially within saidsecond heating chamber and fed by natural draft; said first heatingchamber comprising: a first burner zone generally surrounding said firstburner; a first buffer zone disposed between said first burner zone andsaid griddle surface and generally defined by said griddle surface and adownwardly extending perimeter wall comprising at least a first rearwall portion having a lower edge spaced downwardly from said griddlesurface; wherein hot combustion gases from said first burnersubstantially fill an upper portion of said first buffer zone; andwherein cooling combustion gases from said first buffer zone exhaustunder lower edge of said first rear wall; said second heating chambercomprising: a second burner zone generally surrounding said secondburner; a second buffer zone disposed between said second burner zoneand said griddle surface and generally defined by said griddle surfaceand a downwardly extending perimeter wall comprising at least a secondrear wall portion having a lower edge spaced downwardly from saidgriddle surface; wherein hot combustion gases from said second burnersubstantially fill said second buffer zone; and wherein coolingcombustion gases from said second buffer zone exhaust under lower edgeof said second rear wall.
 17. The device of claim 16 wherein an averagefront-to-back flow rate through said first buffer zone is substantiallyless than an average front-to-back flow rate through said first burnerzone.
 18. The device of claim 16 wherein an average front-to-back flowrate through said first buffer zone is less than about 15% of an averagefront-to-back flow rate through said first burner zone.
 19. The deviceof claim 16 wherein said lower edge of said first rear wall comprises atleast a first section extending lower than a second section thereof, andwherein said second section is disposed closer to a center of saidgriddle surface than said first section.
 20. The device of claim 16wherein said first heating chamber and said second heating chamber sharea common perimeter wall element.
 21. The device of claim 16 wherein saidfirst rear wall portion and said second rear wall portion comprisedifferent sections of the same wall element.
 22. The device of claim 16wherein said cooking device is selected from the group consisting of agriddle and a braising pan.
 23. The device of claim 16 including a plategenerally bounding at least one of said heating chambers on a lower sidethereof, wherein said plate includes a plurality of flow holes thereinfor the inlet of secondary air into said at least one heating chamber.24. The device of claim 23 wherein at least some of said flow holes havea diameter of approximately ⅝ inch and are disposed in a front-to-backdirection generally towards the middle of said at least one heatingchamber.
 25. The device of claim 16 wherein said first heating chamberhas one buffer zone.